Apparatus and method for input of ideographic Korean syllables from reduced keyboard

ABSTRACT

Systems and methods for input of text symbols into an electronic device comprising a reduced keyboard having keys representing a plurality of characters are disclosed. Possible symbol variants are identified based on character inputs received from the reduced keyboard. Each identified symbol variant is grouped into one of a plurality of groups of symbol variants, each group having an associated priority, according to a type of the symbol variant. Within at least one of the groups, the symbol variants are ranked in decreasing order of frequencies of use of the symbol variants. A list of symbol variants comprising the plurality of groups of symbol variants in order of decreasing priority is then displayed, and an input symbol is selected from the list of symbol variants. The symbol variants of the at least one of the groups of symbol variants are thereby sorted by both priority and frequency of use.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority from U.S. Provisional Application Ser.No. 60/393,997, filed on Jul. 3, 2002. The complete disclosure of thisprovisional application, including drawings, is hereby incorporated intothis application by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to data input on electronic devices,and in particular to input of ideographic Korean syllables from reducedkeyboards.

2. Description of the State of the Art

The Korean language, like most Asian languages, is comprised ofthousands of symbols, making it impossible to represent all the symbolson a keyboard. As such, several keystrokes are normally required toenter a single symbol. For example, Korean symbols include basic Jamocharacters, compound Jamo characters, and Hangul syllables. CompoundJamo characters and Hangul syllables are built from basic Jamocharacters. The basic Jamo characters include 19 leading consonants, 21vowels, and 28 trailing consonants, whereas the total number of possibleHangul syllables is 11,172.

When reduced keyboards or keypads containing multiple-character keys,such as those found on electronic devices, are used for Korean textinput, this problem is further compounded. Entry of each basic Jamocharacter typically requires a user to depress a single key multipletimes, and entry of a compound Jamo character or Hangul syllablerequires entry of several basic Jamo characters. Therefore, entry of asingle symbol may require many keystrokes.

In order to alleviate the problem of character composition, inputmethods were designed and developed, containing the required logic forthe Korean language based on composition rules, to convert keystrokes ofusers into appropriate symbols. However, these conversions according toknown input methods are often ambiguous or incorrect, forcing a user toeither select an intended symbol from a plurality of possible symbolsgenerated by the input method or correct an incorrect symbol generatedby the input method. Such symbol selection or correction makes textinput slow and tedious, and the use of devices with reduced keypads veryinconvenient.

SUMMARY

According to an aspect of the invention, a method for input of textsymbols into an electronic device comprising a reduced keyboard havingkeys representing a plurality of characters is provided. The methodcomprises the steps of receiving character inputs from the reducedkeyboard, identifying symbol variants based on the received characterinputs, grouping each symbol variant in one of a plurality of groups ofsymbol variants according to a type of the symbol variant, each of theplurality of groups having an associated priority, ranking the symbolvariants within at least one of the groups of symbol variants indecreasing order of frequencies of use of the symbol variants,displaying a list of symbol variants comprising the plurality of groupsof symbol variants in order of decreasing priority, and selecting aninput symbol from the list of symbol variants, wherein the symbolvariants of the at least one of the groups of symbol variants are sortedby both priority and frequency of use.

A system of inputting text symbols into an electronic device inaccordance with another aspect of the invention comprises a reducedkeyboard having keys representing a plurality of characters forcomposing text symbols, an input queue configured to receive characterinputs from the reduced keyboard, a memory configured to store frequencyof use information for a plurality of symbols, an input processoroperatively coupled to the memory and the input queue and configured toidentify possible symbol variants comprising text symbols at leastpartially composed of the received character inputs, to assign each ofthe symbol variants to one of a plurality of groups of symbol variantshaving associated priorities according to a type of the symbol variant,to sort the symbol variants within at least one of the groups based onthe frequency of use information stored in the memory, and to select aninput symbol from the list of symbol variants, a display; and a userinterface coupled between the display and the input processor to displaya list of symbol variants comprising the groups of symbol variants inorder of decreasing priority on the display.

In a further embodiment of the invention, a computer-readable medium isprovided, the medium storing software code instructions for inputtingtext symbols into an electronic device comprising a reduced keyboardrepresenting a plurality of characters, the software code instructionscomprising instructions for performing the functions of receivingcharacter inputs from the reduced keyboard, identifying symbol variantsbased on the received character inputs, grouping each symbol variant inone of a plurality of groups of symbol variants according to a type ofthe symbol variant, each of the plurality of groups having an associatedpriority, ranking the symbol variants within at least one of the groupsof symbol variants in decreasing order of frequencies of use of thesymbol variants, displaying a list of symbol variants comprising theplurality of groups of symbol variants in order of decreasing priority,and selecting an input symbol from the list of symbol variants, whereinthe symbol variants of the at least one of the groups of symbol variantsare sorted by both priority and frequency of use.

Further features of the invention will be described or will becomeapparent in the course of the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an example of a basic leading consonant.

FIG. 2 shows an example of a compound leading consonant.

FIG. 3 shows an example of a basic medial vowel.

FIG. 4 shows an example of a compound medial vowel.

FIG. 5 shows an example of a basic trailing consonant.

FIG. 6 shows an example of a compound trailing consonant.

FIG. 7 is a block diagram showing a reduced keyboard which includes bothbasic consonants and vowels.

FIG. 8 is a block diagram of another reduced keyboard, with a reducedkey layout including all the basic consonants.

FIG. 9 shows an example of composition of a compound leading consonantfrom the basic leading consonants.

FIG. 10 shows an example of composition of a compound medial vowel fromthe basic leading consonants.

FIG. 11 shows an example of composition of a compound trailing consonantfrom the basic leading consonants.

FIG. 12 shows a Hangul syllable having a leading consonant, a medialvowel and a trailing consonant.

FIG. 13 shows a Hangul syllable that having a leading consonant and amedial vowel.

FIG. 14 illustrates composition of a Hangul syllable from compoundcharacters.

FIGS. 15( a) and 15(b) show two keys from the reduced keyboard of FIG.7.

FIG. 16 shows a lookup window with variants sorted using frequencyprediction.

FIG. 17 shows a lookup window without frequency prediction.

FIG. 18 is a block diagram of a data structure for storing frequency ofuse information for Hangul syllables.

FIG. 19 is a block diagram of a data structure for storing frequency ofuse information for leading consonants.

FIG. 20 is a flow diagram illustrating a method of inputting Koreansyllables from a reduced keyboard.

FIG. 21 is a block diagram of a system of inputting Korean syllables.

FIG. 22 shows a correspondence array between Korean Hangul syllables andChinese Hanzi syllables.

FIG. 23 shows an array of offsets in the correspondence array of FIG.22.

FIG. 24 shows a jumping table for a frequency data structure.

FIG. 25 shows a lookup window displaying a plurality of groups of symbolvariants.

DETAILED DESCRIPTION

As described above, symbols in the Korean language include basic Jamocharacters, compound Jamo characters, and Hangul syllables. The basicJamo characters are used to build the compound Jamo characters and theHangul syllables. All of the Jamo characters, including both basic andcompound Jamo characters are covered by the Unicode range 0x1100–0x11F9.These Jamo characters are classified into three categories, according totheir position in a sequence of text input. Examples of characters ineach category are shown in FIGS. 1–6 and described below.

A “choseong” character is a leading consonant or syllable-initialcharacter. FIG. 1 shows an example of a basic leading consonant, andFIG. 2 shows an example of a compound leading consonant. Choseongcharacters reside in the Unicode range 0x1100–0x1159. The leadingconsonants shown in FIGS. 1 and 2 are Unicode characters 0x1100 and0x1101, respectively.

Examples of “jungseong” characters, also known as medial vowels orsyllable-peak characters, are shown in FIGS. 3 and 4. FIG. 3 shows anexample of a basic medial vowel, and FIG. 4 shows an example of acompound medial vowel. Unicode characters 0x1161 and 0x1164 are shown inFIGS. 3 and 4, although medial vowels occupy the Unicode range0x1160–0x11A2.

FIGS. 5 and 6 show an example of a basic trailing consonant and anexample of a compound trailing consonant. Basic trailing consonants,also referred to a “jongseong” characters or syllable-final characters,are found in the Unicode range 0x11A8–0x11F9. Unicode characters 0x11F9and 0x11B5 are shown in FIGS. 5 and 6.

The leading, medial, and trailing categories, as well as the level ofcomplexity of a character, basic or compound, are important for reducedkeyboards. As those skilled in the art will appreciate, reducedkeyboards are generally implemented in electronic devices to conservespace where the size of the device is to be minimized. Mobile telephonesand other mobile communication devices, personal digital assistants(PDAs), and remote controls are examples of electronic devices thatinclude reduced keyboards.

Reduced keyboards for Korean input may include consonants or bothconsonants and vowels. Since compound Jamo characters and Hangulsyllables can be built from basic Jamo characters, reduced keyboardstypically include basic characters only. FIG. 7 is a block diagramshowing a reduced keyboard which includes both basic consonants andvowels.

The reduced keyboard 10 of FIG. 7 comprises a plurality ofmultiple-character keys 12, each multiple-character key having two ormore basic Jamo characters. Associating multiple characters with eachmultiple-character key 12 allows a number of characters to berepresented on the reduced keyboard 10 with fewer keys than the numberof characters. Although the reduced keyboard 10 includes only 10multiple-character keys 12, 24 characters are represented. As describedin further detail below, the multiple-character keys 12 may be used toinput many more characters and symbols in accordance with aspects of theinvention.

The reduced keyboard 10 also includes a punctuation key 13, which isused to enter punctuation marks. Other common keyboard keys provided inthe reduced keyboard 10 include a space bar 14, a backspace key 15, adelete key 16, a shift key 17, and an enter key 18. Navigation of acursor on a display screen of an electronic device when data is beingentered using the reduced keyboard 10 is enabled by the arrow keys 20.

The homonym key 22 is used when a user wishes to replace a composedKorean Hangul syllable with a corresponding Chinese Hanzi character, aswill be described in further detail below.

FIG. 8 is a block diagram of another reduced keyboard, with a reducedkey layout including all the basic consonants. The reduced keyboard 30is substantially the same as the reduced keyboard 10, including aplurality of keys 32, at least some of which are multiple-characterkeys, a punctuation key 33, a space bar 34, a backspace key 35, a deletekey 36, a shift key 37, an enter key 38, arrow keys 40, and a homonymkey 42. However, character assignments for the reduced keyboard 30differ from those of the reduced keyboard 10, in that the reducedkeyboard 30 includes all of the basic Jamo consonants. Using the reducedkeyboard 30, basic vowels are composed from the basic consonants.

Compound Jamo characters and Hangul syllables can be built or composedfrom the basic Jamo characters represented on a reduced keyboard, suchas the reduced keyboard 10 or 30. FIG. 9 shows an example of compositionof a compound leading consonant from the basic leading consonants. InFIG. 9, the compound leading consonant 0x1101, shown at 56, is composedusing the basic leading consonant 0x1100, shown at 52 and 54, byentering the basic leading consonant 0x1101 twice.

FIGS. 10 and 11 show further examples of compound Jamo charactercomposition. FIG. 10 shows an example of composition of a compoundmedial vowel from the basic leading consonants, wherein the medial vowel0x1166, shown at 62, is composed from the basic medial vowels 0x1165, at58, and 0x1175, at 60. FIG. 11 shows an example of composition of acompound trailing consonant from the basic leading consonants. In FIG.11, the compound trailing consonant 0x11B5 (68) is composed from thebasic trailing consonants 0x11AF (64) and 0x11C1 (66).

The other compound Jamo characters are composed using the basic Jamocharacters in a similar manner.

All of the 11,172 Hangul syllables reside in the 0xAC00–0xD7A3 Unicoderange, and are also composed from Jamo characters. Each Hangul syllablecan be represented by a sequence of Jamo characters entered in a givenorder. There are two formats of Hangul syllable, shown in FIGS. 12 and13.

FIG. 12 shows a Hangul syllable having a leading consonant, a medialvowel and a trailing consonant. This format of Hangul syllable,abbreviated “LVT”, for leading consonant, medial vowel and trailingconsonant, includes the Unicode character 0xAC10. FIG. 13 shows a Hangulsyllable that having a leading consonant and a medial vowel, which isabbreviated herein to an “LV” syllable. Unicode character 0XAC00 is anexample of an LV Hangul syllable.

The systems and methods described herein provide for inputtingideographic Korean characters and syllables from reduced keyboards.Compound symbols, including both compound Jamo characters and Hangulsyllables, that are not represented on reduced keyboards are composedfrom a limited set of characters that are represented on the keyboards.

Conversion of a Jamo character sequence to Hangul syllables followscomposition rules and procedures. In compound character composition,each step of user input generated by depressing keys on a keyboard isbased on previous user input, which includes one or more charactersdepending upon the key mapping of the particular reduced keyboard,conversion rules, and frequency of use for Hangul syllable, Jamocharacters, and different composition formats. According to Koreangrammar rules, Jamo characters are used only in composition of Hangulsyllables. Therefore, although a user provides inputs to composesequences of Jamo characters, the result of user inputs is a series ofHangul syllables.

As described above, all of the Hangul syllables have either an LV or anLVT format, each of which has a corresponding input scheme or charactersequence. In both cases, the user begins input with a leading consonant.Compound consonants (both leading and final) are not normallyrepresented on reduced keyboards, but can be composed from basiccharacters represented on a reduced keyboard. For example, as shown inFIG. 9, the consonant compound leading consonant 0x1101 is the result ofa double input of the basic consonant character 0x1100. Following aleading consonant, a medial vowel is expected. Compound medial vowelsare also not typically represented on the reduced keypads, but can becomposed from a sequence of basic vowel character inputs, as shown inFIG. 10.

At this point, the user input may be completed, because there are Hangulcharacters that are composed with the LV scheme, such as the Hangulsyllable “GA”, 0xAC00, in FIG. 13. Otherwise, input of a trailingconsonant is expected when an LVT Hangul syllable such as the Hangulsyllable “GAM” 0xAC10 (FIG. 12), is composed with the LVT scheme.

The Hangul syllables shown in FIGS. 12 and 13 are composed from basicJamo characters. However, many Hangul syllables include one or morecompound Jamo characters. This type of Hangul syllable is composed bysequentially entering basic characters in a sequence such that eachbasic and/or compound character is composed in the order that theyappear in the desired Hangul syllable. FIG. 14 illustrates compositionof a Hangul syllable from compound characters.

As shown in FIG. 14, the “GGELP” Hangul syllable 0xAEE6, 70, is composedthe compound Jamo characters 0x1101 (56), 0x1166 (62), and 0x11B5 (68).Using a reduced keyboard on which only basic Jamo characters arerepresented, the Jamo character 0x1101 is composed by a double entry ofthe basic character 0x100, as shown in FIG. 9 and described above. Thecompound Jamo characters 0x1166 and 0x11B5 are similarly composed usinga reduced keyboard by entering the basic characters 0x1165 and 0x1175(FIG. 10), and 0x11AF and 0x11C1 (FIG. 11). Thus, the Hangul syllableAEE6 may be composed by a user by making keystrokes on a reducedkeyboard to enter the following basic Jamo characters: 0x1100, 0x1100,0x1165, 0x1175, 0x11AF, and 0x11C1.

A primary shortcoming of known input systems and methods for reducedkeyboards is ambiguity in conversion from user input sequences of basiccharacters into ideographic Korean symbols. As described above, knownsystems and methods often require a user to select or correct symbolsgenerated in response to user inputs.

It should be apparent from the foregoing that a sequence of charactersinput by a user may be converted into several types of input symbols,including Hangul syllables, compound Jamo characters, basic Jamocharacters as input by the user, and sequences of characters that cannotbe used as a basis of composition because they do not meet Koreangrammar rules. According to an aspect of the invention, the user ispresented with a list of choices of possible input symbol variants basedon characters entered by the user. Symbol variants are ordered in thelist based on sorting rules described in further detail below.

The variants for any sequence of basic characters input by a user arefirst grouped and ranked according to a priority based on the type ofthe variant. Hangul syllables have the highest priority. Second priorityis given to compound Jamo characters, which are not Hangul syllables butare the result of correct user input of basic characters. Third priorityis given to the basic Jamo characters input by the user. Last prioritybelongs to Jamo characters sequences that do not meet Korean grammarrules.

For each variant in at least some of the groups, a correspondingfrequency of use is found, and the variants in each group are thenranked, within the group, by frequency of use. Variants are therebyranked first by priority and then by frequency. For example, a Hangulsyllable having a higher frequency of use than other variants that arealso Hangul syllables has the highest overall priority and occurs firstin a list of variants presented to a user. Hangul syllables, sorted byfrequency, are listed first, followed in order of priority by anyvariants in the other groups, sorted in order of frequency within eachgroup. The list of variants represents input predictions based onpriority and, for at least some of the symbol variant groups, frequencyof use of each symbol variant. In one embodiment of the invention,described in further detail below, both a Hangul syllable group and aleading consonant group are sorted by frequency. However, ranking byfrequency of use offers little advantage for some of the symbol variantgroups, such as sequences of characters that violate grammar rules.Although a user might occasionally wish to input this type of sequence,such sequences are generally used infrequently. Thus, storage offrequency of use information for these sequences and frequency-basedranking of these sequences could be avoided without significantlysacrificing the performance of the Korean syllable input system andmethod.

FIG. 25 shows a lookup window 200 displaying a plurality of groups ofsymbol variants 202, 204, 206, 208 and 210 prioritized and ranked asdescribed above. The variants 202, 204, 206, 208 and 210 may begenerated by a reduced keyboard similar to those shown in FIGS. 7 and 8.The variants 202 may have the highest priority and comprise a Hangulsyllable identified by unicode value 0xAc1c (

). The second variants 204 may have the second highest priority andcomprise a basic Jamo character identified by the unicode values 0x 1100(

) and a compound Jamo character identified by the unicode value 0x1162 (

). The third variants 206 may have the third highest priority andcomprise a basic Jamo characters identified by the unicode values 0x1100(

), 0x1161 (

), and 0x1175 (|). The fourth variants 208 may have the fourth highestpriority and comprise Jamo character sequences that violate Koreangrammar rules, e.g., the basic Jamo characters identified by the unicodevalues 0x1100 (

), 0x110f (

), 0x318D (•), and 0x1175 (|). The fifth variants 210 may have the leasthighest priority and comprise another Jamo character sequence thatviolate Korean grammar rules, e.g., the basic Jamo character identifiedby the unicode values 0x1100 (

), compound Jamo character identified by the unicode value 0x1162 (

), and the basic jamo character identified by the unicode value 0x110f (

). At least one of the groups of symbol variants 202, 204, 206, 108 and210 maybe further ranked by frequency of use.

Priority- and frequency-based prediction is an accurate and reliablemechanism that enables user input in Korean on electronic devices havingreduced keyboards, making interaction with such devices more convenientand faster relative to known input systems and methods. The followingexample, with reference to FIGS. 15–17, illustrates the differencesbetween input prediction schemes according to aspects of the inventionand known input prediction schemes.

FIGS. 15( a) and 15(b) show two keys from the reduced keyboard 10 ofFIG. 7. The keys in FIGS. 15( a) and 15(b) are both multiple-characterkeys 12 found in the top row of the reduced keyboard 10 (FIG. 7). Themultiple-character key 72 represents the characters 0x100 and 0x1161,and the multiple-character key 74 represents the characters 0x1103 and0x1165. In order to input the Hangul syllable “GGEO” (0xAEBC) using thekeyboard 10 of FIG. 7, the user depresses the key 72, and then the key74. As described above, the Hangul syllable GGEO is composed from thecompound Jamo character 0x1101, which can be composed from a doubleentry of the basic Jamo character 0x1100. According to an aspect of theinvention, however, grammar rules and frequencies of use are used toidentify possible symbol variants based on fewer keystrokes, such thatthe key 72 need only be depressed once, even though the desired Hangulsyllable includes a compound leading consonant.

As shown in FIGS. 15( a) and 15(b), each of the keys 72 and 74represents two characters. Therefore, four different input sequences arepossible. Based on these input sequences, many more variants arepossible. As described above, Hangul syllables, compound Jamocharacters, basic Jamo characters, and sequences of characters that donot meet Korean grammar rules are all possible symbol variants when auser makes keystrokes using a reduced keyboard. When the user depressesthe key 72, for example, it is possible that either of the basic Jamocharacters 0x1100 or 0x1161 is intended, even though the Jamo character0x1161, a medial vowel, violates Korean grammar rules if used on its ownwithout a leading consonant. The character 0x1100, a leading consonant,may be used on its own as a basic leading consonant, or as a first basiccharacter for composition of a compound leading consonant, to compose aHangul syllable.

The key 74 represents the characters 0x1103, a basic leading consonant,and 0x1165, a basic medial vowel. The basic leading consonant 0x1103might be intended on its own as the leading consonant in a next Hangulsyllable, or as an initial basic character for composition of a compoundleading consonant in the next Hangul syllable. The basic medial vowel0x1165 could be intended as a basic medial vowel or part of a compoundmedial vowel, where the entry of the key 72 was intended to compose acompound leading consonant, for example.

For each possible basic Jamo character input, several compound Jamocharacters and Hangul syllables may also be identified.

Clearly, the keystroke sequence of 72, 74 generates many possiblevariants. Each variant is identified based on the characters representedon the particular keys depressed and Korean language composition rulesfor LV and LVT Hangul syllables. Although other variants are possible,only two such variants are considered below for the purposes ofillustration.

FIG. 16 shows a lookup window with variants sorted using frequencyprediction. As shown in FIG. 16, the homonym lookup window 76 includestwo symbol variants, 78 and 80. Both variants 78 and 80 interpret thekeystroke of the key 72 as a composition of the compound Jamo character0x1101. In the variant 78, which is the intended Hangul syllable GGEO,the subsequent keystroke of key 74 is interpreted as input of the medialvowel 0x1165 for composition of a Hangul syllable. The variant 80,however, is generated by interpreting the keystroke of key 74 as inputof the leading consonant 0x1103. Although this is one possible symbolvariant, the variant 80 is a character sequence that violates Koreangrammar rules and cannot be used to compose a Hangul syllable, becauseit includes only a leading consonant and a trailing consonant, without amedial vowel.

In the lookup window 76, the variants are sorted according to thepriority scheme described above, such that the Hangul syllable GGEOranks higher in the list than the sequence of the Jamo characters 0x1101and 0x1103. Where more than one symbol variant is a Hangul syllable,frequency of use information is obtained for each Hangul syllable, andthe Hangul syllable variants are sorted according to frequency of use.Where frequency of use information is available for other symbol variantgroups, symbols variants in these groups are similarly ranked byfrequency of use.

FIG. 17 shows a lookup window without frequency prediction. In thelookup window 82, the variants are the same as shown in FIG. 16,although they have been sorted in a different order, as shown at 84 and86. According to known techniques, variants are presented in an order inwhich they are stored in a memory, a “first found” scheme, or dependentupon the particular character mapping of multiple-character keys on areduced keyboard. The intended input Hangul GGEO appears second in thelookup window 82, and a user must therefore select the intended inputHangul syllable. This selection may be made, for example, by using thearrow keys 20 on the keyboard 10 (FIG. 7) to move a cursor to theintended input text, in this case a Hangul syllable, and pressing theenter key 38. Those skilled in the art will appreciate that other typesof input devices, including a thumbwheel, for example, may be used forinput selection, where such input devices are provided in an electronicdevice.

According to an aspect of the invention, the first entry in a lookupwindow is preferably selected by default and displayed at a current textentry position on a text input screen on a display. Unless a userselects another variant, then the first entry is selected as an inputwhen it is determined that composition of a Hangul syllable is complete,as described in further detail below. The user continually types as longas intended inputs are generated in the lookup window and displayed onthe text input screen. Priority- and frequency-based ranking of variantsprovides reliable and accurate prediction of intended inputs, increasingthe ease and speed of Korean text entry from reduced keyboards.

Three data structures are preferably used for composition of leadingconsonants, medial vowels and trailing consonants. These data structuresare correspondence arrays between basic Jamo characters and compoundJamo characters. Each correspondence array is stored in a memory on anelectronic device and used to identify possible input variants when auser provides inputs using a reduced keyboard.

Although Unicode numbers for each Jamo character may be used to indexarray elements, memory space requirements for these arrays may bereduced by normalizing indexes in the arrays with LBase, VBase andTBase, the Unicode numbers for the first leading consonant, medialvowel, and trailing consonant, respectively. Since Jamo charactersoccupy contiguous Unicode ranges, each Jamo character may be uniquelyidentified by a respective normalized index which indicates its positionin the Unicode range. For example, the first leading consonant having aUnicode number of 0x1100 may be identified with the index 0 where LBaseis selected as 0x1100. However, it should be apparent that other indexschemes may instead be used to identify Jamo characters.

One embodiment of a correspondence array with indexes generated asdescribed above, for compound leading consonants is as follows:

-   -   {0x1100-LBase, 0x1100-LBase, 0x1101-LBase},    -   {0x1103-LBase, 0x1103-LBase, 0x1104-LBase},    -   {0x1107-LBase, 0x1107-LBase, 0x1108-LBase} . . .

For compound medial vowels, a similar correspondence array is shownbelow:

-   -   {0x1161-VBase, 0x1169-VBase, 0x116A-VBase},    -   {0x1162-VBase, 0x1169-VBase, 0x116B-VBase},    -   {0x1175-VBase, 0x1169-VBase, 0x116C-VBase} . . .

A correspondence array for trailing consonants can similarly begenerated as follows:

-   -   {0x11A8-TBase, 0x11A8-TBase, 0x11A9-TBase},    -   {0x11A8-TBase, 0x11BA-TBase, 0x11AA-TBase},    -   {0x11AB-TBase, 0x11BD-TBase, 0x11AC-TBase} . . .

Although correspondences between basic and compound Jamo characters areknown to those familiar with the Korean language, these arrays ofindexes provide a compact data structure for storage of thesecorrespondences.

In the above example of a user entering the GGEO Hangul from a reducedkeyboard by entering a keystroke sequence of 72, 74 (see FIGS. 15( a)and 15(b)), the leading consonant correspondence array is searched afterthe key 72 has been depressed, and the corresponding compound character0x1101 is identified as a possible variant. Generally, the compoundcharacter correspondence arrays are searched when a user has inputcharacters that may be used to compose a compound character. Asdescribed above, although the key 72 represents two basic characters,the only possible compound leading consonant that a user might becomposing is 0x1101. When character indexes for the leading consonantcorrespondence array are generated using LBase=0x1100, the first entryin the array is {0x00, 0x00, 0x01}. In this example, an input using thekey 72 translates into an input of 0x00. For this input, the array entry{0x00, 0x00, 0x01} is found, and the compound leading consonant havingan index of 0x01 is identified as a variant for that input.

Compound symbol variants for medial vowels are identified in a similarmanner, where input keystrokes could possibly be intended to composecompound medial vowels. When the key 72 is depressed, a leadingconsonant is expected, since this is the first character input.Following a leading consonant, either another basic leading consonant,to compose a compound leading consonant, or a basic medial vowel is avalid input. As such, when the key 74 is then depressed, the basicmedial vowel, 0x1165, could be intended as a medial vowel or as a firstbasic vowel for composing a compound medial vowel. The input of 0x1165translate into index 0x05 when VBase=0x1160. The medial vowelcorrespondence array is searched to determine whether a compound medialvowel corresponds to the sequence of basic vowels, by determiningwhether any entry in the array begins with index 0x05. In this example,the medial vowel correspondence array would include an entry for atleast the compound medial vowel 0x1166, as {0x05, 0x05, 0x06}, since thebasic character 0x1165 (index 0x05) can be used to compose the compoundmedial vowel 0x1166 (index 0x06).

It should be appreciated that other input sequences are also possible.For example, the entry using the key 72 could be interpreted as entry ofthe medial vowel 0x1161 (index 0x01), and the subsequent entry using thekey 74 could be interpreted as entry of the medial vowel 0x1165 (index0x05), even though such an input sequence violates Korean grammar rules.In this case, the medial vowel correspondence array would not include anentry beginning with 0x01, 0x05, since these basic characters do notform a compound medial vowel.

For trailing consonants, similar operations are performed to identifypossible compound symbol variants.

Compound character variants identified in this manner are grouped andpossibly ranked as described above, and presented to the user in alookup window with other symbol variants. The particular display methodis dependent upon the type of electronic device in which the Koreaninput is enabled. Where the display method is dependent upon Unicodenumber, for example, Unicode numbers for identified compound charactervariants can be regenerated simply by adding the appropriate basenumber, LBase, VBase, or TBase, to the correspondence array indexes forthe identified variants.

When at least leading consonant variants have been identified, Hangulsyllable variants can be predicted. Any Hangul syllable which includesone of the leading consonant variants is itself a Hangul syllablevariant for the input sequence. Frequency of use information for eachHangul syllable variant is then obtained, and the Hangul syllablevariants are ranked in decreasing order of frequency of use, with theHangul syllable variant having the highest frequency of use being rankedhighest and thus occurring first in a lookup window or list of variants.

Frequency of use information, at least initially, comprises informationindicative of how often each particular symbol is used. This informationmay be available from a variety of sources, including existinghistorical linguistic pattern records, for example. More targeted oruser-specific frequency of use information may instead be generated onthe basis of particular collections of Korean text. However, the presentinvention is in no way limited to frequency of use information from anyparticular source. Provided that the frequency of use information for atleast one of the groups of variants is available during Korean textinput, its source is not important.

In order to rank symbol variants based on frequency of use, frequency ofuse information for at least one of the symbol variant groups is storedon an electronic device. According to an embodiment of the invention,frequency of use information is stored for at least Hangul syllables.FIG. 18 is a block diagram of a data structure for storing frequency ofuse information for Hangul syllables.

The Hangul syllable frequency data structure 100 comprises a pluralityof pairs of 2-byte Hangul syllable numbers and 2-byte frequencies ofuse. In FIG. 18, three such pairs 102/104, 106/108, and 110, 112 areshown as representative examples. Intervening pairs between the secondpair 106/108 and the last pair 110/112 correspond to other respectiveHangul syllables but have a similar structure.

Each Hangul syllable number in the data structure 100 uniquelyidentifies a Hangul syllable. Unicode numbers for Hangul syllables havebeen established and are preferably used in the data structure 100.However, other types of identifiers may instead be used in a frequencydata structure. For example, since Hangul syllables reside in acontiguous Unicode range, each Hangul syllable can be identified with anindex indicating its position in the Unicode range instead of theUnicode number. In order to represent each Hangul syllable, this indexmust be at least 14 bits in length, resulting in a saving of 2 bits ofmemory space per number/frequency pair. Where frequency of useinformation is stored for all Hangul syllables, the index itself neednot be stored. In this situation, the position of a frequency of useentry for a Hangul syllable in an array of frequencies of useinformation corresponds to the index of the Hangul syllable. However,storage of syllable numbers or indexes in the frequency data structure100 enables storage of frequency of use information for fewer than allof the Hangul syllables, to thereby conserve memory space. Syllablenumbers also avoid the necessity of maintaining a particular order ofentries, which is difficult where entries are added to and deleted fromthe frequency data structure 100.

Frequency of use information in the frequency data structure 100 ispreferably a measure of relative frequency of each Hangul syllable. Forexample, the Hangul syllable having the highest frequency of use mayhave a frequency of use of 0, to indicate that it is the first Hangulsyllable in decreasing order of frequency of use. The second mostfrequently used Hangul syllable then has a frequency of use of 1, and soon. In this manner, frequency of use information can be stored using thesame number of bits as the Hangul numbers or indexes. Those skilled inthe art will appreciate that absolute frequencies or numbers ofoccurrences of each syllable in a particular collection of Korean textused to generate frequency of use information, for example, or othertypes of relative frequencies of use may instead be stored in thefrequency data structure 100.

Those skilled in the art will appreciate that several techniques may beused to identify possible Hangul syllable variants once leadingconsonants variants, and possibly medial vowel and trailing consonantvariants, have been identified. A correspondence array or table,although relatively simple to implement and support, requiressignificant memory resources, as described above. Alternatively,mathematical algorithms may be used to determine Hangul syllables basedon Jamo character variants. Using these algorithms and Unicode numbers,or possibly other indexes or identifiers, of Jamo characters, Unicodenumbers, indexes, or identifiers of possible Hangul syllables arecalculated. Where numbers resulting from such calculations representvalid Hangul syllables, the numbers are translated if necessary,depending upon how Hangul syllables are identified in the Hangulsyllable frequency data structure 100, and used to access correspondingfrequency of use information in the frequency data structure 100.

As described above, Jamo characters are used to compose Hangul syllablesfor input of Korean text. Jamo characters are not used on their own inKorean text. Therefore, a Korean syllable input system and methodaccording to aspects of the present invention could be implemented usingsymbol variant sorting, and thus frequency of use information, forHangul syllables only. In such an implementation, symbol variants arepreferably grouped by type of symbol to maintain the priority rankingdescribed above, but only variants in the Hangul syllables group arethen ranked based on frequency of use.

In other embodiments, frequency of use information may also be storedfor other types of symbol variants. FIG. 19 is a block diagram of a datastructure for storing frequency of use information for leadingconsonants. The leading consonant frequency data structure 120 includesfrequency of use information for leading consonants, a first, second,and last of which are shown at 114, 116 and 118. In the data structure120, the frequency of use of each leading consonant is preferably arelative frequency of use, and is thus stored in a single byte. Relativefrequency of use information in any data structure could be stored inmore or less than one byte, depending upon the total number of symbolsfor the data structure. Consonant numbers or indexes are not necessaryin the data structure 120, since frequency of use information is storedfor every leading consonant. For example, as described above, leadingconsonants occupy a contiguous Unicode range and can be identified by anindex. Frequency of use entries for each leading consonant can then bearranged in the data structure 120 such that the frequency of useinformation at a particular position in the data structure 120 relatesto the leading consonant having the corresponding index.

Prediction accuracy generally improves with the amount of frequency ofuse information available. This improved accuracy is provided at thecost of additional memory space to accommodate more frequency of useinformation. Therefore, when implementing Korean syllable input systemsor methods as described herein, trade-offs are made between predictionaccuracy and memory requirements. If sufficient memory space isavailable, then frequency of use information for Hangul syllables andeach type of Jamo character could be stored. Where memory space islimited or should be conserved, then frequency of use information couldbe stored only for Hangul syllables, or even just a certain number ofthe most frequently used Hangul syllables.

FIG. 20 is a flow diagram illustrating a method of inputting Koreansyllables from a reduced keyboard. The method begins at step 22 whereuser inputs are received and buffered. Since symbol predictions arebased on one or more preceding inputs, as described above, at least twoinputs are received from the user at step 122. When two or more inputshave been received at step 122, symbol variants are identified based onthese inputs, at step 124. Symbol variants for a particular sequence ofinputs may include Hangul syllables, compound Jamo characters, basicJamo characters, and sequences of characters that cannot be used to formvalid Korean text.

The identified variants are then grouped at step 126 by type of symbol.Hangul syllables are the highest priority group, followed by compoundJamo characters, basic Jamo characters, and character sequences thatviolate grammar rules. Variants in each group for which frequency of useinformation is available are then ranked by frequency of use, at step128. Frequency of use information is available for at least Hangulsyllables. When a Hangul syllable variants are identified, based on Jamocharacter variants, the frequency of use of each identified variant isobtained from the Hangul syllable frequency data structure. The Hangulsyllables are then ranked in order of decreasing frequency of use. Wherefrequency of use information is available for other groups of symbolvariants, the variants in these groups are similarly ranked.

As will be apparent from the above description of frequency datastructures, frequency of use information may be available for only somevariants in a group. For example, frequency of use information could bestored only for a predetermined number of most frequently used Hangulsyllables, or perhaps for only one type of Jamo characters, such asleading consonants. In these situations, variants for which no frequencyof use information is available are preferably ranked below those forwhich frequency of use information is available. This effectivelyassumes a zero frequency of use, or some other predetermined frequencyof use lower than the lowest available frequency of use for variants inthe same group, for these variants.

At step 130, a list of variants is displayed to a user, in a lookupwindow as described above, a menu, or some other pick list type ofinterface. The symbol variant having the highest overall ranking, aHangul syllable if any Hangul syllable variants were identified at step124, is also inserted at a current text entry position on a text inputscreen. It is then determined, at step 132, whether the user has made asymbol selection from the list of variants. The method proceeds at step134 to receive a further keyboard input from the user at step 134 wherethe user has not made a symbol selection from the list of variants.Although initial and further user input steps are shown as separatesteps 122 and 134, a user may continue to provide keyboard inputs whilevariants are being identified and ranked where the inputs are buffered,and the further input is then obtained from the buffer at step 134. Forexample, in one embodiment a text input system, user inputs are bufferedin an input queue, such that step 134 involves receiving the furtherkeyboard input from the input queue.

A determination is then made at step 136 whether the user has started tocompose a new Hangul syllable. This determination is based on both thefurther user input received at step 134 and previous user inputs. Wherethe most recent user input was a medial vowel or trailing consonant, forexample, and the further input is a leading consonant, then the user isentering characters to compose a new Hangul syllable. In this case, thebuffer of previous inputs is cleared at step 142. The operationsinvolved in clearing the input buffer are dependent upon how the bufferis implemented. Where the buffer is a circular queue, for example,previous inputs might not actually be deleted, but are eventuallyoverwritten with subsequent inputs.

Processing then returns to step 122, where one or more new user inputsare received and buffered. Variants based on these inputs areidentified, grouped, ranked and displayed, as described above.Composition of a new Hangul syllable at step 136 is also determined whena space bar on a reduced keyboard is depressed by the user. In thiscase, the further input need not be considered when identifyingvariants, and the method instead awaits two or more new inputs at step122.

Where it is determined at step 136 that a new Hangul syllable is notbeing composed, such as where a backspace key or a keyboard key mappedto a medial vowel or trailing consonant, is input by the user, forexample. If the further user input is generated by depressing a keyboardkey representing one or more characters, then the method is repeatedtaking the further input into account to thereby provide an updated listof variants. Although new variants might be identified, grouped, ranked,and displayed at steps 124–130, a more likely result of the furtherinput is to reduce the number of symbol variants. For example, manyHangul syllable variants may be possible based on a particular compoundleading consonant composed using two initial user inputs received atstep 122, whereas only a subset of such variants are possible when thefurther character is a medial vowel. In this situation, some variantsare effectively removed from the list of variants. Where a maximum sizeis imposed on the list of variants, less frequently variants notdisplayed in a previous list of variants could also be added to the listof variants. If the further input is generated by the user by depressinga backspace key to remove an unintended or erroneous user entry, thenthe list of variants will likely be expanded. Although not explicitlyshown in FIG. 20, where a backspace operation removes all previousentries, or all but one previous entry, being used to identify symbolvariants, then processing returns to step 122 to await additional userinput.

The user may select an intended symbol from the list of variants anytime after a list of variants is first displayed. Where the user makessuch a selection, as determined at step 132, the selected symbol isinput to the electronic device and replaces the currently displayedhighest-ranked symbol on the input screen. In order to provide for ameasure of frequency of use adaptation or learning based on actual userinput patterns, the frequency of selected symbols is preferablyincreased at step 140. Frequency of use data based on historicalpatterns or particular collections of Korean text might not be suitablefor every situation or for every user. Step 140 provides a mechanismwhereby symbols that are used frequently by a user eventually attain ahigher ranking within their respective symbol groups. Although step 140assumes that frequency of use information is available for the type ofsymbol selected, frequency of use information may, alternatively, becreated when a symbol is selected by the user.

When a symbol is selected, then a current syllable composition operationis complete, and any subsequent user inputs must be intended to composea new Hangul syllable. Previous inputs used to compose the selectedsymbol are therefore cleared at step 142, and the input method awaitsuser inputs at step 122.

FIG. 21 is a block diagram of a system of inputting Korean syllables.The system of FIG. 21 includes a reduced keyboard 151, an input queue152, a user interface 153, an input processor 154, a memory 155, and adisplay 156, all implemented in an electronic device 150.

The reduced keyboard 151 includes keys which represent some, but notall, characters used for input of Hangul syllables. The keyboards shownin FIGS. 7 and 8 are examples of reduced keyboards, although theinvention is in no way restricted to these, or any other, particularreduced keyboards. In the electronic device 150, user inputs from thereduced keyboard 151 are received by the input queue 152. These inputsare buffered in the input queue 152 as described above.

The user interface 153 provides an interface to the user of theelectronic device 150. It accepts inputs from the user via the reducedkeyboard 151, and also provides outputs to the user via the display 156.The user interface 153 displays, for example, a text input screen forcomposing Korean text, and list of Korean symbol variants, on thedisplay screen 156.

The input processor 154 receives buffered inputs from the input queue152, through the user interface 153, and identifies symbol variantsbased on the inputs. The input processor 154 also assigns the identifiedsymbol variants into groups and accesses frequency of use informationfor at least one of the groups of symbols stored in the memory 155. Thesymbol variants in each group for which frequency of use information hasbeen stored in the memory 155 are then sorted in order of decreasingfrequency of use. An input symbol is selected from the list of symbolvariants by the input processor 154, responsive to either a symbolselection by a user or the start of a new symbol, as described above.

The memory 155 comprises one or more data stores and is implementedusing one or more types of storage component. Electronic devices such as150 typically include both writeable memory, Random Access Memory (RAM)for example, and Read Only Memory (ROM), from which data may only beread. Writeable memory may be either volatile or non-volatile, althoughnon-volatile memory such as Flash RAM or battery backed-up RAM ispreferred when any data in the writeable memory should be maintained inthe event of loss of power. The above correspondence arrays, the Hangulsyllable frequency data structure, and any other frequency datastructures are stored in the memory 155, preferably in non-volatilememory, and accessed as necessary when Korean text is being input to theelectronic device. If the system of FIG. 21 supports learning oradaptation of frequency of use information, then frequency datastructures are preferably stored in non-volatile writeable memory.Otherwise, frequency of use information may instead be stored in ROM.

The input queue 152, although shown as a separate block in FIG. 21, mayactually be provided in writeable memory in the memory 155. The inputqueue 152 need not be in non-volatile memory, because it stores userinputs for only a single Hangul syllable at any time. The memory 155 mayalso store data for other systems on the electronic device 150,operating system software for the electronic device 150, and possiblysoftware applications, modules and utilities which provide variouselectronic device functions. Korean text input techniques as describedherein may be implemented, for example, as software instructions in asoftware application or a software module configured to operate inconjunction with one or more software applications to enable Korean textinput for processing by such software applications.

The display 156 provides visual data output to a user of the electronicdevice 150. In portable electronic devices, for example, liquid crystaldisplays are often used.

User inputs for entering Korean text on the electronic device 150 aremade by depressing keys on the reduced keyboard 151. Text entry may beinvoked by the user, for example, by starting a particular softwareapplication, module, or utility, using a particular function supportedon the electronic device 150. Whenever an operation or function requiresinput of Korean text, the Korean text input system processed user inputsto predict correct Korean Hangul syllables. Where more than one softwareapplication supports text input, for example, the Korean text inputsystem is preferably implemented as a software module or utility thatcan be called or invoked by any of the software applications.Alternatively, each such software application may incorporate softwareinstructions to perform Korean text input as described herein.

As will be apparent, the user interface 153 presents a text entry screenon the display 156 to aid in text entry. The particular content andformatting of the text entry screen is dependent, for example, upon thenature of the text being entered, the function for which text is beingentered, or the software application currently in use. Text is displayedon the text entry screen as it is predicted by the Korean text entrysystem or selected by the user.

When user inputs have been received, the input processor 154 identifiessymbol variants based on these inputs. Correspondence arrays stored inthe memory 155 are accessed to identify compound leading consonant,medial vowel, and trailing consonant variants. Possible Hangul syllablevariants are also identified. As described above, the input processor154 groups the identified variants by type of symbol, and accessesfrequency data structures in the memory 155 to sort the variants in eachgroup for which frequency of use information is available.

A sorted list of variants is then displayed to a user on the display156. As described above, the highest ranked symbol variant is alsopreferably displayed in a current position in the text entry screen. Thesorted list of variants, although displayed on the same display 156 asthe text entry screen, preferably does not obscure the user's view ofthe current position of the text entry screen. Alternatively, since thehighest ranked variant is displayed in both the sorted list of variantsand at the current position of the text entry screen, the Korean textentry system may be configured such that the sorted list of variants isdisplayed on the display 156 such that the highest ranked variant in thesorted list is displayed at the current position of the text entryscreen. The position of the highest ranked variant in the sorted listthen effectively overlies the current position of the text entry screen,such that the user sees the highest ranked variant at only one positionon the text entry screen, and can more easily view both the highestvariant and other variants in the sorted list at the current position inthe text entry screen.

In response to selection of a symbol variant from the sorted list, theinput processor 154 replaces the highest ranked symbol variant with theselected symbol at the current position in the text entry screen,updates the frequency of use information for the selected symbol iflearning or adaptation is enabled, and clears the input queue 152.Selection of a symbol from the list may be accomplished, for example,using navigation keys on the reduced keyboard 151, or, alternatively, anauxiliary input device (not shown) such as a thumbwheel.

If the user does not select a symbol from the sorted list of variants,then the input processor 154 determines whether the user has started tocompose a new Hangul syllable based on a further user input receivedfrom the reduced keyboard 151. Where a new Hangul syllable is beingcomposed, the input queue 152 is cleared, and new symbol variants areidentified, grouped, ranked, and displayed. Otherwise, the current listof variants is updated based on the further user input.

Although the above description refers to functions performed by theinput processor 154, it will be appreciated by those skilled in the artthat these functions of the input processor 154 are directed by softwareinstructions in a software application, module, or utility in which aKorean text input method is implemented.

It will be appreciated that the above description relates to preferredembodiments by way of example only. Many variations on the systems andmethods described above will be obvious to those knowledgeable in thefield, and such obvious variations are within the scope of the inventionas described and claimed, whether or not expressly described.

For example, those skilled in the art will appreciate that the Unicodestandard recognizes both Old and New Jamo characters. A further datastructure enables conversion of Old Jamo characters to New Jamocharacters and vice versa. This data structure is preferably acorrespondence array similar to the compound Jamo charactercorrespondence arrays described above, having the following structure:

-   -   {0x1100, 0x3131},    -   {0x1101, 0x3132},    -   {0x1102, 0x3134},    -   {0x1103, 0x3137} . . .

The first number in each entry in the above array is a Unicode number ofan Old Jamo character, and the second number in each entry is theUnicode number of the corresponding New Jamo character. Correspondencebetween Old and New Jamo characters is not a strict correspondencebetween Unicode ranges, as is apparent from the above examplecorrespondence array entries, but the character correspondence is fixed.

This Jamo replacement feature is enabled on an electronic device bystoring the above correspondence array in memory on the electronicdevice and accessing the memory when an entered Old Jamo character is tobe replaced by its corresponding New Jamo character. A Korean text inputsystem or method may be configured to search the correspondence arrayand replace each Old Jamo character with its corresponding New Jamocharacter, if one exists, as Old characters are entered. Alternatively,character replacement may be configured as a function or utility thatmust be invoked by a user before or during each text entry operation.Although Unicode numbers are shown in the array above, indexes mayinstead be used, since both the Old Jamo characters and the New Jamocharacters respectively reside in the contiguous Unicode ranges0x1100–0x11FF and 0x3131–0x318E. For example, Old Jamo character indexesmay be generated by subtracting the Unicode number of the first Old Jamocharacter (0x1100) from the Unicode number of each Old Jamo characterwhich has a corresponding New Jamo character. New Jamo character indexesmay similarly be generated by subtracting the Unicode number of thefirst New Jamo character (0x3131) from the Unicode number of each NewJamo character. Each entry in the Old/New Jamo character correspondencearray are then only 4 bytes (a pair of 1-byte indexes) instead of 8bytes (a pair of 2-byte Unicode numbers).

In addition, some of the Korean Hangul syllables can also be representedby Homonyms, which are Chinese Hanzi syllables. Replacement of Hangulsyllables with Hanzi syllables is similarly enabled by further arraydata structures. These data structures are shown in FIGS. 22 and 23.

FIG. 22 shows a correspondence array between Korean Hangul syllables andChinese Hanzi syllables. The array 160 is a static array of homonymsthat contains Korean Hangul syllables and corresponding Chinese Hanzisyllables. For any Korean Hangul syllable, such as 162 and 166, theremay be a number of possible corresponding Hanzi syllables, designated164 and 168.

FIG. 23 shows an array of offsets in the correspondence array of FIG.22. Each element 172, 174, 176,178, as well as elements between 176 and178, in the array of offsets 170 corresponds to the index of Koreansyllables in the correspondence array 160. These arrays are used to findHanzi syllable variants for a Korean syllable. Preferably, a userinvokes Hangul/Hanzi syllable replacement on a per-syllable basis aftera Hangul syllable has been entered, by depressing the homonym key on akeyboard, for example. The reduced keyboards shown in FIGS. 7 and 8include a homonym key for this purpose. However, corresponding Hanzisyllable variants may instead be identified each time a Korean syllablethat appears in the correspondence array is entered by a user. In thekeyboards.

Searching of Hanzi syllables based on input of a Korean syllable isbased on a correspondence between elements of two arrays. When a KoreanHangul syllable is input and the user invokes the syllable replacementfunction, an index of the Hangul syllable is searched in the array ofoffsets. The element at that index is the index of the Korean Hangulsyllable in the correspondence array 160. The group of Chinese Hanzisyllable variants with which the Hangul syllable may be replaced followsthe Hangul syllable in the array of sequences. The number of elements inthe group of variants can be calculated as one less than the differencebetween the values of two elements in the array of offsets. For thefirst Hangul syllable 0xAC01 at index 0, for example, the Hanzisyllables 164 are all possible variants with which the Hangul syllablemay be replaced. Since the Hangul syllable 0xAC08 appears in thecorrespondence array at index 10, as shown in the array of offsets 170at 174, the Hanzi syllables 164 occupy indexes 1 through 9 in thecorrespondence array 160. This number of Hanzi syllable variants canalso be calculated as the difference between the offset at the index ofthe Hangul syllable to be replaced, 0 in this example, and the offset atthe next index in the array of offsets, which is 10 in this example,less 1. The Hanzi syllable variants identified in the correspondencearray are then displayed to the user, and the user then selects theintended Hanzi syllable, with which the Hangul syllable is replaced.

Frequency of use information could be stored for all Hangul syllables, acertain number of most frequently used Hangul syllables, or Hangulsyllables having frequencies of use above a predetermined threshold.When frequency of use information for fewer than all Hangul syllables isstored, then searching speed of the frequency data structure 100 shownin FIG. 18 can be increased by providing a jumping table or similar datastructure which indicates the position and size of any “gaps” infrequency of use information in the frequency data structure. FIG. 24shows a jumping table for a frequency data structure. The jumping table180 includes pairs of elements 182/184, 186/188, 190/192, as well asintervening elements not explicitly shown in FIG. 24. Each paircomprises a starting index and a length for each gap in a frequency datastructure. Where the jumping table is used for searching the Hangulsyllable frequency data structure, the first index 82 corresponds to theUnicode number or index of the first Hangul syllable for which nofrequency of use information has been stored. The length then specifiesthe length of the gap, as either a number of entries or a Unicode numberof the last consecutive Hangul syllable in the gap, for which nofrequency of use information exists in the data structure. Using gapindexes and lengths in the jumping table, frequency of use informationfor a symbol can be located without sequentially searching the frequencydata structure. Where a Hangul syllable falls within one of the gapsindicated in the jumping table, the frequency data structure need not besearched at all. Otherwise, a section of the frequency data structure inwhich frequency of use information for the Hangul syllable is found isquickly identified based on the indexes and lengths of the gaps. Searchspeed for other frequency data structures may similarly be optimized,although the additional memory space required for storage of a furtherdata structure is generally feasible only for relatively large datastructures, for which sequential search time, and thus search timesavings, can be significant.

The keyboards 10 and 30 are shown in FIGS. 7 and 8 for illustrativepurposes only. Where an electronic device provides an auxiliarynavigation input device such as a thumbwheel, for example, arrow keys 20need not be provided on the reduced keyboard 10. Korean input systemsand methods according to aspects of the invention are also independentof any particular key mapping on a reduced keyboard.

The components shown in the electronic device 150 are similarlyillustrative, and an electronic device in which a Korean text input isenabled may include other components in addition to those shown in FIG.22. These additional components are dependent upon the type ofelectronic device, but may include, for example, one or more of awireless transceiver configured to operate within a wirelesscommunication network, a voice communication module, a datacommunication module, a plurality of software applications, any of aplurality of types of communication interfaces, and a power source suchas a battery. The various arrays and data structures described above maybe loaded onto such an electronic device via any suitable interface,such as a wireless transceiver, a serial port, a Universal Serial Bus(USB) port, a disk drive or other memory reading device, an infraredport, an 802.11 module, or a Bluetooth™ module. Those skilled in the artwill appreciate that “802.11” and “Bluetooth” refer to sets ofspecifications, available from the Institute for Electrical andElectronics Engineers (IEEE), relating to wireless local area networksand wireless personal area networks, respectively.

1. A method for input of text symbols into an electronic devicecomprising a reduced keyboard, the reduced keyboard having keysrepresenting a plurality of characters, the method comprising the stepsof: receiving character inputs from the reduced keyboard; identifyingsymbol variants based on the received character inputs; grouping eachsymbol variant in one of a plurality of groups of symbol variantsaccording to a type of the symbol variant, each of the plurality ofgroups having an associated priority; ranking the symbol variants withinat least one of the groups of symbol variants in decreasing order offrequencies of use of the symbol variants; displaying a list of symbolvariants comprising the plurality of groups of symbol variants in orderof decreasing priority; and selecting an input symbol from the list ofsymbol variants, wherein the symbol variants of the at least one of thegroups of symbol variants are sorted by both priority and frequency ofuse; wherein the text symbols comprise Korean text symbols, and whereinthe plurality of groups of symbol variants comprise a Hangul syllablesgroup, a compound Jamo characters group, a basic Jamo characters group,and a group of sequences of characters that violate Korean grammarrules.
 2. The method of claim 1, wherein the character inputs comprisecharacters used to compose the symbol variants.
 3. The method of claim1, wherein the symbol variants comprise Korean Hangul syllables.
 4. Themethod of claim 1, wherein the at least one of the groups of symbolvariants comprises the group having a highest priority.
 5. The method ofclaim 1, wherein the step of selecting comprises the step of receiving asymbol selection input from a user of the electronic device.
 6. Themethod of claim 1, implemented in computer software instructions.
 7. Themethod of claim 1, wherein the step of ranking comprises the steps of:accessing stored frequency of use information for each of the symbolvariants in the at least one of the groups of symbol variants; andsorting the symbol variants within the at least one of the groups ofsymbol variants based on the frequency of use information.
 8. The methodof claim 7, wherein the step of accessing further comprises the stepsof, for each of the symbol variants in the at least one of the groups ofsymbol variants: determining whether frequency of use information hasbeen stored in a frequency data structure for the symbol variant;retrieving the frequency of use information where frequency of useinformation has been stored in a frequency data structure for the symbolvariant; and assuming predetermined frequency of use information wherethe frequency of use information has not been stored in the frequencydata structure for the symbol variant.
 9. The method of claim 1, whereinthe step of selecting comprises the steps of: receiving a furthercharacter input from a user of the electronic device; determiningwhether the further character input is related to a current text symbolor a new text symbol; and selecting a first symbol variant in the listof symbol variants as the input symbol where the further character inputis related to the new text symbol.
 10. The method of claim 9, furthercomprising the step of repeating the steps of identifying, grouping,ranking, and displaying where the further character input is related tothe current text symbol.
 11. The method of claim 1, wherein the Hangulsyllables group has a highest priority among the plurality of groups.12. The method of claim 11, wherein the compound Jamo characters grouphas a higher priority than the basic Jamo characters group, and whereinthe group of sequences of characters that violate Korean grammar ruleshas a lowest priority among the plurality of groups.
 13. The method ofclaim 11, wherein the at least one of the groups of symbol variantscomprises the Hangul syllables group.
 14. A system of inputting textsymbols into an electronic device, comprising: a reduced keyboard havingkeys representing a plurality of characters for composing text symbols;an input queue configured to receive character inputs from the reducedkeyboard; a memory configured to store frequency of use information fora plurality of symbols; an input processor operatively coupled to thememory and the input queue and configured to identify possible symbolvariants comprising text symbols at least partially composed of thereceived character inputs, to assign each of the symbol variants to oneof a plurality of groups of symbol variants having associated prioritiesaccording to a type of the symbol variant, to sort the symbol variantswithin at least one of the groups based on the frequency of useinformation stored in the memory, and to select an input symbol from thelist of symbol variants; a display; and a user interface coupled betweenthe display and the input processor to display a list of symbol variantscomprising the groups of symbol variants in order of decreasing priorityon the display; wherein the plurality of characters include Korean Jamocharacters, and wherein the plurality of groups comprise a Korean Hangulsyllable group, a compound Jamo character group, and a basic Jamocharacter group.
 15. The system of claim 14, wherein the keys includeone or more multiple-character keys, each multiple-character keyrepresenting more than one character.
 16. The system of claim 14,wherein the user interface is further configured to display a text inputscreen on the display, the text input screen comprising a current textinput position, and to display a first symbol variant in the list ofsymbol variants at the current text input position.
 17. The system ofclaim 14, wherein the input processor selects an input symbol from thelist of variants by: receiving a further input from the input queue;determining whether the further input is a symbol selection inputindicating a selected symbol variant in the list of symbol variants;selecting the selected symbol as the input symbol as the input symbolwhere the further input is a symbol selection input indicating aselected symbol variant in the list of symbol variants; determiningwhether the further input is a character input related to a current textsymbol or a new text symbol where the further input is not a symbolselection input indicating a selected symbol variant in the list ofsymbol variants; and selecting a first symbol variant in the list ofsymbol variants as the input symbol where the further input is acharacter input related to the new text symbol.
 18. A computer-readablemedium storing software code instructions for inputting text symbolsinto an electronic device comprising a reduced keyboard representing aplurality of characters, the software code instructions comprisinginstructions for performing the functions of: receiving character inputsfrom the reduced keyboard; identifying symbol variants based on thereceived character inputs; grouping each symbol variant in one of aplurality of groups of symbol variants according to a type of the symbolvariant, each of the plurality of groups having an associated priority;ranking the symbol variants within at least one of the groups of symbolvariants in decreasing order of frequencies of use of the symbolvariants; displaying a list of symbol variants comprising the pluralityof groups of symbol variants in order of decreasing priority; andselecting an input symbol from the list of symbol variants, wherein thesymbol variants of the at least one of the groups of symbol variants aresorted by both priority and frequency of use; wherein the text symbolscomprise Korean text symbols, and wherein the plurality of groups ofsymbol variants comprise a Hangul syllables group, a compound Jamocharacters group, a basic Jamo characters group, and a group ofsequences of characters that violate Korean grammar rules.